Patches for s_expl.c

Stephen Montgomery-Smith stephen at
Wed May 29 01:21:19 UTC 2013

On 05/28/2013 07:06 PM, Steve Kargl wrote:
> On Tue, May 28, 2013 at 06:17:46PM -0500, Stephen Montgomery-Smith wrote:
>> On 05/28/2013 05:53 PM, Steve Kargl wrote:
>>> Given that I've merged, unmerged, remerged, disremerged, and
>>> undisremerged numerous diffs over the last 2+ years, I am not
>>> surprise that there are issues with the patches.  I'm neither
>>> an expert in floating arithmetic nor style(9).  If I understand
>>> half of what you write when you annotate one of your diffs, I 
>>> feel lucky.
>>> (Un)fortunately, I only have a few hours this week to work on
>>> expl/expm1l, and then I'll disappear again for a month or two
>>> (due to work and life).  (Un)fortunately, theraven (under the
>>> pretense of core) has threaten to completely rendered libm into
>>> a crippled useless mess by mapping all unimplemented long double
>>> functions to their double cousins.  When/if it comes to pass
>>> that I have to untangle whatever theraven does, I'll likely
>>> just walk away from libm hacking.
>> I think it is better to commit "as is" if you cannot make all the changes.
>> As for me, I don't really understand the need to be so consistent with
>> style, nor to get every last drop of optimization.  In particular,
>> regarding style, I think it is like people talking different languages.
>>  You could insist that everyone speak a common language, but it is far
>> better for the intellectual commons if people learn other peoples'
>> languages.
>> Anyway, I think it is better for Steve to commit, and then for Bruce to
>> make changes later on.
> It's too late.  In making some change since the last time I test
> has introduced a massive regression in the computation of expm1l.
> laptop-kargl:kargl[204] ./testl -n 5 -b
> prec: 64
> For x in [-64.0000:-0.1659], 5M expm1l calls in 2.176513 seconds.
> For x in [-0.1659:0.1659], 5M expm1l calls in 0.415051 seconds.
> For x in [0.1659:11356.0000], 5M expm1l calls in 0.550342 seconds.
> Notice, the first interval is now 4 to 5 times slower than the
> other intervals.  This was not the case with an older version
> of the code.
> :(

I think it is still better to commit.  Then figure out where the
regression was later, when you have time.

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